1. Field of Use
This invention relates generally to a one-piece molded plastic anchor nut for insertion in a mounting hole in a workpiece and adapted to receive a screw or other threaded member, such as a threaded adjustable mounting foot for an object, such as a domestic appliance or piece of furniture or the like.
2. Description of the Prior Art
Various types of anchor nuts of the aforedescribed general character are known and in use and the following U.S. and foreign patents illustrate the state of the art: U.S. Pat. No. 4,284,378; U.S. Pat. No. 3,741,067; U.S. Pat. No. 3,508,593; U.S. Pat. No. 2,785,726; U.S. Pat. No. 3,789,724; U.S. Pat. No. 4,358,234; U.S. Pat. No. 4,077,300; U.S. Pat. No. 3,449,799; German 25 46 831; Swiss 319871. U.S. Pat. No. 3,508,593 discloses a nut having a bore in which threads are tapped or cut as a screw is driven thereinto. U.S. Pat. No. 4,284,378 discloses a nut which comprises integrally formed foldable component parts which cooperate to define the nut and in which a screw-receiving bore is provided in which threads appear to be cut as a screw is inserted. U.S. Pat. No. 3,741,067 discloses a fastening assembly comprising a pair of complementary plastic nut-halves which are joined to a threaded member by webs. In use, the nut-halves are folded around the screw and the assembly is inserted into a mounting hole in a workpiece, whereupon initial rotation of the screw effects severance of the webs and allows the screw to be positioned as desired. U.S. Pat. No. 2,785,726 discloses one version wherein an expanded insert adapted for insertion into a hole in a panel has a plurality of outwardly movable legs which define a threaded bore for engagement with a free-running screw.
U.S. Pat. No. 3,789,724 discloses a foldable nut in which the inner surface of each foldable section includes molded depression, including threaded and unthreaded portions, and a pair of integrally molded loops which are threaded on the inside surface thereof. Furthermore, the latching means which retain the nut in a hole in a workpiece include projection on two opposite sides and each projection extends the entire width of the nut shank. A slot is disposed between the nut bore and the projection and also extends the entire width of the nut shank. U.S. Pat. No. 4,358,234 discloses a one-piece non-foldable initially unthreaded retaining clip. U.S. Pat. No. 4,077,300 discloses a one-piece non-foldable initially unthreaded grommet. U.S. Pat. No. 3,449,799 discloses a one-piece non-foldable fastener with a tapered bore and screw-expandable legs. German Pat. No. 25 46 831 discloses a metal nut formed in two halves and apparently held together by a sleeve. Swiss Pat. No. 319871 discloses a non-reusable multi-section foldable soft-metal plate which folds to define an anchor nut which expands when a screw is inserted therein.
The prior art also discloses an arrangement wherein metal anchor nuts in the form of "weldnuts" (TM) are spot-welded to the frame of an object, such as an appliance or piece of furniture, thus providing a threaded hole into which a metal foot having a threaded shank is power driven. The mounting feet are adjustable and are used to level the object when in use as well as in some instances to secure the object to a shipping pallet during shipping. In some instances, however, the feet are not used to mount the object on the pallet during shipping, but instead are merely screwed up out of the way against the anchor nut. Installation of anchor nuts by welding has always been a problem and often results in a high reject rate that is very costly. In addition, when the threaded foot is power driven into the nut, rejects occur due to stripped and damaged threads, if the threaded foot is not in exact alignment with the nut. It is desirable, therefore, to directly replace such weldnuts by anchor nuts not requiring a welding operation or a power driving operation that results in so many rejects.
At present there are some plastic fasteners or anchor nuts available that overcome some of the above problems but they are costly due to either a need for a secondary tapping operation to provide threads therein, or due to a weaker part having lesser thread engagement than is desirable because of the special construction.